This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This is a phase II protocol for children with newly diagnosed, diffuse intrinsic brain stem gliomas. Capecitabine RDT dosing during the radiation phase will be 650 mg/m2 administered twice daily and is based on the pediatric MTD of capecitabine with concomitant RT from the phase I pediatric trial. There should be no interruptions in capecitabine administration in the absence of unacceptable adverse event. Oral capecitabine RDT will continue for a total of nine weeks, followed by a two-week break. Post-RT therapy will begin after the two week break. Post radiation therapy, patients will receive twice daily oral capecitabine for 3 courses. During each course, capecitabine will be administered for 14 consecutive days followed by a 7-day rest period. Capecitabine will be provided as a flavored, film coated, rapidly disintegrating tablet that may be swallowed intact or dispersed in water for patients unable to swallow tablets.